The invention relates to a system of at least first and second apparatuses interconnected for the communication of control messages by means of a serial data channel, the first apparatus having:
user input means defining a plurality of keys for activation by a user, and PA1 first control means responsive to the user commands, including means for identifying a user command which requires to be processed by a second control means located in the second apparatus of the system, and means for in such a case generating a control message conveying the received user command to said second apparatus via the serial data channel, PA1 at least one functional element; and PA1 second control means for receiving via the serial data channel control messages conveying user commands received by the user input means of the first apparatus and for processing the conveyed user command to control the functional element(s) of the second apparatus in accordance with the user's wishes. PA1 user input means defining a plurality of keys for activation by a user, the defined keys including "normal" keys for which each activation implies a single user command and "repeat" keys for which a prolonged activation implies a repetitive series of user commands for the duration of the activation; and PA1 first control means responsive to the user commands, including means for identifying a user command which requires to be processed by a second control means located in the second apparatus of the system, and means for in such a case generating a control message conveying the received user command to said second apparatus via the serial data channel, PA1 at least one functional element; and PA1 second control means for receiving via the serial data channel control messages conveying user commands received by the user input means of the first apparatus and for processing the conveyed user command to control the functional element(s) of the second apparatus in accordance with the user's wishes,
the second apparatus including:
The invention further relates to apparatuses suitable for use in such a system.
A system as set forth above is described in EP 0 423 739 A2, where the apparatuses are domestic audio/video apparatuses and a shared control bus provides the serial data channel between two apparatuses. The keys are provided on a wireless remote control handset, to which more than one "first apparatus" may respond. This first reference describes means to prevent multiple actions occurring in response to a single activation of a key on the handset. Such action can conveniently be regarded as a form of de-bouncing.
An alternative means for de-bouncing in a similar system is described in European Patent application 92200856.0 not published at the priority date of the present application, whose contents are incorporated herein by reference. Again the serial data channel is provided by a shared bus, namely a Domestic Digital Bus (D2B). D2B has been standardised by the International Electrotechnical Commission, and provides for control of any connected apparatus by any other, being in other words a multi-master system with distributed control. "D2B" is a registered trade mark of Philips Electronics NV.
In this second reference it is described how a prolonged activation of the "volume-up" key on the remote control handset, implies a series of "volume up" commands, occurring repeatedly at a certain frequency until the key is released. Each repetition causes an increase of one step in the volume setting of the audio apparatus being controlled. In fact it is possible in the user input means of many known apparatuses to distinguish between this repeating type of key such as "volume up", "brightness down" etc., and a normal type of key, for which each activation implies just one user command, whatever its duration. Examples of "normal" keys are "1", "2", "play", "stop" and "standby".
A third reference is the European Home Systems Specification, Release 1.1, published by the European Home Systems Association, Eindhoven, NL. The specification provides for bus messages conveying key activations and, optionally, for a generic "key released" message.
In the systems described in the references, however, no distinction is made between user command messages conveying activation of "repeat" keys and those relating to "normal" keys. As described in the second reference, therefore, the prolonged activation of the "volume up" key results in repeated user command messages being generated on the shared bus, for example every 100 milliseconds. This rate of repetition is of course well within the capabilities of the D2B bus, but excess bus traffic should generally be avoided if possible. Moreover, if two or three apparatuses all respond to activation of a key on the same wireless remote control handset, the bus traffic is immediately multiplied two- or three-fold, irrespective of any de-bouncing mechanism. The resulting processing effort required of the control means of the second apparatus can also become a substantial overhead.
Yet further problems arise when it is desired to extend the principles of the user command techniques described in the references to provide inter-operation between apparatuses from different manufacturers (so-called "inter-brand compatibility"), or even between different models from the same manufacturers. The frequency of command repetition varies widely from manufacturer to manufacturer, from less than 5 per second in some present systems to perhaps 20 per second in future systems. At the same time, the number of discrete steps in, say, the volume adjustment of one television may be widely different to that of another television from the same or a different manufacturer. The number of steps can also be different for volume, brightness, contrast and other settings within one apparatus. Thus, the prior art techniques can lead to unpredictable performance in multi-brand systems.